6.3.E: Specific Adaptive Host Defenses (Exercises)
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18.1: Architecture of the Immune System
Adaptive immunity is defined by two important characteristics: specificity and memory. Specificity refers to the adaptive immune system’s ability to target specific pathogens, and memory refers to its ability to quickly respond to pathogens to which it has previously been exposed. For example, when an individual recovers from chickenpox, the body develops a memory of the infection that will specifically protect it from the causative agent if it is exposed to the virus again later.
Multiple Choice
Antibodies are produced by ________.
- plasma cells
- T cells
- bone marrow
- B cells
- Answer
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A
Cellular adaptive immunity is carried out by ________.
- B cells
- T cells
- bone marrow
- neutrophils
- Answer
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B
A single antigen molecule may be composed of many individual ________.
- T-cell receptors
- B-cell receptors
- MHC II
- epitopes
- Answer
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D
Which class of molecules is the most antigenic?
- polysaccharides
- lipids
- proteins
- carbohydrates
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C
Matching
Match the antibody class with its description.
| ___IgA | A. This class of antibody is the only one that can cross the placenta. |
| ___IgD | B. This class of antibody is the first to appear after activation of B cells. |
| ___IgE | C. This class of antibody is involved in the defense against parasitic infections and involved in allergic responses. |
| ___IgG | D. This class of antibody is found in very large amounts in mucus secretions. |
| ___IgM | E. This class of antibody is not secreted by B cells but is expressed on the surface of naïve B cells. |
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d, e, c, a, b
Fill in the Blank
There are two critically important aspects of adaptive immunity. The first is specificity, while the second is ________.
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memory
________ immunity involves the production of antibody molecules that bind to specific antigens.
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Humoral
The heavy chains of an antibody molecule contain ________ region segments, which help to determine its class or isotype.
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constant
The variable regions of the heavy and light chains form the ________ sites of an antibody.
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antigen-binding
Short Answer
What is the difference between humoral and cellular adaptive immunity?
What is the difference between an antigen and a hapten?
Describe the mechanism of antibody-dependent cell-mediated cytotoxicity.
18.2: Antigens, Antigen Presenting Cells, and Major Histocompatibility Complexes
Major histocompatibility complex (MHC) molecules are expressed on the surface of healthy cells, identifying them as normal and “self” to natural killer (NK) cells. MHC molecules also play an important role in the presentation of foreign antigens, which is a critical step in the activation of T cells and thus an important mechanism of the adaptive immune system.
Multiple Choice
MHC I molecules present
- processed foreign antigens from proteasomes.
- processed self-antigens from phagolysosome.
- antibodies.
- T cell antigens.
- Answer
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A
MHC II molecules present
- processed self-antigens from proteasomes.
- processed foreign antigens from phagolysosomes.
- antibodies.
- T cell receptors.
- Answer
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B
Which type of antigen-presenting molecule is found on all nucleated cells?
- MHC II
- MHC I
- antibodies
- B-cell receptors
- Answer
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B
Which type of antigen-presenting molecule is found only on macrophages, dendritic cells, and B cells?
- MHC I
- MHC II
- T-cell receptors
- B-cell receptors
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B
Fill in the Blank
MHC molecules are used for antigen ________ to T cells.
- Answer
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presentation
MHC II molecules are made up of two subunits (α and β) of approximately equal size, whereas MHC I molecules consist of a larger α subunit and a smaller subunit called ________.
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β 2 microglobulin
Critical Thinking
Which mechanism of antigen presentation would be used to present antigens from a cell infected with a virus?
Which pathway of antigen presentation would be used to present antigens from an extracellular bacterial infection?
18.3: T Lymphocytes
The antibodies involved in humoral immunity often bind pathogens and toxins before they can attach to and invade host cells. Thus, humoral immunity is primarily concerned with fighting pathogens in extracellular spaces. However, pathogens that have already gained entry to host cells are largely protected from the humoral antibody-mediated defenses. Cellular immunity, on the other hand, targets and eliminates intracellular pathogens through the actions of T lymphocytes, or T cells.
Multiple Choice
What is a superantigen?
- a protein that is highly efficient at stimulating a single type of productive and specific T cell response
- a protein produced by antigen-presenting cells to enhance their presentation capabilities
- a protein produced by T cells as a way of increasing the antigen activation they receive from antigen-presenting cells
- a protein that activates T cells in a nonspecific and uncontrolled manner
- Answer
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D
To what does the TCR of a helper T cell bind?
- antigens presented with MHC I molecules
- antigens presented with MHC II molecules
- free antigen in a soluble form
- haptens only
- Answer
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B
Cytotoxic T cells will bind with their TCR to which of the following?
- antigens presented with MHC I molecules
- antigens presented with MHC II molecules
- free antigen in a soluble form
- haptens only
- Answer
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A
A ________ molecule is a glycoprotein used to identify and distinguish white blood cells.
- T-cell receptor
- B-cell receptor
- MHC I
- cluster of differentiation
- Answer
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D
Name the T helper cell subset involved in antibody production.
- T H 1
- T H 2
- T H 17
- CTL
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B
Fill in the Blank
A ________ T cell will become activated by presentation of foreign antigen associated with an MHC I molecule.
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cytotoxic
A ________ T cell will become activated by presentation of foreign antigen in association with an MHC II molecule.
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helper
A TCR is a protein dimer embedded in the plasma membrane of a T cell. The ________ region of each of the two protein chains is what gives it the capability to bind to a presented antigen.
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variable
Peripheral tolerance mechanisms function on T cells after they mature and exit the ________.
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thymus
Both ________ and effector T cells are produced during differentiation of activated T cells.
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memory
Short Answer
What is the basic difference in effector function between helper and cytotoxic T cells?
What necessary interactions are required for activation of helper T cells and activation/effector function of cytotoxic T cells?
18.4: B Lymphocytes and Antibodies
Humoral immunity refers to mechanisms of the adaptive immune defenses that are mediated by antibodies secreted by B lymphocytes, or B cells. This section focuses on B cells and discusses their production and maturation, receptors, and mechanisms of activation.
Multiple Choice
Which of the following would be a T-dependent antigen?
- lipopolysaccharide
- glycolipid
- protein
- carbohydrate
- Answer
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C
Which of the following would be a BCR?
- CD4
- MHC II
- MHC I
- IgD
- Answer
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D
Which of the following does not occur during the lag period of the primary antibody response?
- activation of helper T cells
- class switching to IgG
- presentation of antigen with MHC II
- binding of antigen to BCRs
- Answer
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B
Fill in the Blank
________ antigens can stimulate B cells to become activated but require cytokine assistance delivered by helper T cells.
- Answer
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T-dependent
T-independent antigens can stimulate B cells to become activated and secrete antibodies without assistance from helper T cells. These antigens possess ________ antigenic epitopes that cross-link BCRs.
- Answer
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repetitive
Critical Thinking
A patient lacks the ability to make functioning T cells because of a genetic disorder. Would this patient’s B cells be able to produce antibodies in response to an infection? Explain your answer.
18.5: Vaccines
By artificially stimulating the adaptive immune defenses, a vaccine triggers memory cell production similar to that which would occur during a primary response. In so doing, the patient is able to mount a strong secondary response upon exposure to the pathogen—but without having to first suffer through an initial infection. In this section, we explore several different kinds of artificial immunity along with various types of vaccines and their mechanisms for inducing artificial immunity.
Multiple Choice
A patient is bitten by a dog with confirmed rabies infection. After treating the bite wound, the physician injects the patient with antibodies that are specific for the rabies virus to prevent the development of an active infection. This is an example of:
- Natural active immunity
- Artificial active immunity
- Natural passive immunity
- Artificial passive immunity
- Answer
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D
A patient gets a cold, and recovers a few days later. The patient's classmates come down with the same cold roughly a week later, but the original patient does not get the same cold again. This is an example of:
- Natural active immunity
- Artificial active immunity
- Natural passive immunity
- Artificial passive immunity
- Answer
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A
Matching
Match each type of vaccine with the corresponding example.
| ___inactivated vaccine | A. Weakened influenza virions that can only replicate in the slightly lower temperatures of the nasal passages are sprayed into the nose. They do not cause serious flu symptoms, but still produce an active infection that induces a protective adaptive immune response. |
| ___live attenuated vaccine | B. Tetanus toxin molecules are harvested and chemically treated to render them harmless. They are then injected into a patient’s arm. |
| ___toxoid vaccine | C. Influenza virus particles grown in chicken eggs are harvested and chemically treated to render them noninfectious. These immunogenic particles are then purified and packaged and administered as an injection. |
| ___subunit vaccine | D. The gene for hepatitis B virus surface antigen is inserted into a yeast genome. The modified yeast is grown and the virus protein is produced, harvested, purified, and used in a vaccine. |
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C, A, B, D
Fill in the Blank
A(n) ________ pathogen is in a weakened state; it is still capable of stimulating an immune response but does not cause a disease.
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attenuated
________ immunity occurs when antibodies from one individual are harvested and given to another to protect against disease or treat active disease.
- Answer
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Artificial passive
In the practice of ________, scabs from smallpox victims were used to immunize susceptible individuals against smallpox.
- Answer
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variolation
Short answer
Briefly compare the pros and cons of inactivated versus live attenuated vaccines.